Elastin-based copolymers and method of using

ABSTRACT

A copolymer comprising a block of an elastin pentapeptide and method of making and using the copolymer are provided.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional application of U.S. application Ser. No. 11/449,896 filed Jun. 9, 2006, the teaching of which is incorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention generally relates to elastin-based copolymers for coating an implantable device such as a drug delivery stent or for forming a composition as cell therapy carrier.

2. Description of the Background

Blood vessel occlusions are commonly treated by mechanically enhancing blood flow in the affected vessels, such as by employing a stent. Stents are used not only for mechanical intervention but also as vehicles for providing biological therapy. To effect a controlled delivery of an active agent in stent medication, the stent can be coated with a biocompatible polymeric coating. The biocompatible polymeric coating can function either as a permeable layer or a carrier to allow a controlled delivery of the agent.

The existing polymeric coating on a stent can have different types of limitations. For example, some poly(ester amide) based coatings can have poor mechanical properties so as to compromise coating integrity, and coating based on hydrophobic polymers can have problems in controlling release of a hydrophilic drug.

Therefore, there is a need for new carrier materials for controlled delivery of an agent. There is a further need for coating materials for coating a medical device.

The polymer and methods of making the polymer disclosed herein address the above described problems.

SUMMARY OF THE INVENTION

Described in this invention is an elastin-based copolymer. The copolymer can be used to form a coating on a medical device. In some embodiments, the coating can further include a polymer, a biobeneficial material, a bioactive agent, or combinations of these. Some examples of the bioactive agent include, but are not limited to, paclitaxel, docetaxel, estradiol, nitric oxide donors, super oxide dismutases, super oxide dismutases mimics, 4-amino-2,2,6,6-tetramethylpiperidine-1-oxyl (4-amino-TEMPO), tacrolimus, dexamethasone, rapamycin, rapamycin derivatives, 40-O-(2-hydroxy)ethyl-rapamycin (everolimus), 40-O-(3-hydroxy)propyl-rapamycin, 40-O-[2-(2-hydroxy)ethoxy]ethyl-rapamycin, and 40-O-tetrazole-rapamycin, 40-epi-(N1-tetrazolyl)-rapamycin (ABT-578), pimecrolimus, imatinib mesylate, midostaurin, clobetasol, mometasone, bioactive RGD, CD-34 antibody, abciximab (REOPRO), progenitor cell capturing antibody, prohealing drugs, prodrugs thereof, co-drugs thereof, or a combination thereof.

A medical device having a coating described herein can be used to treat, prevent, or ameliorate a vascular medical condition. Some exemplary vascular medical conditions include atherosclerosis, thrombosis, restenosis, hemorrhage, vascular dissection or perforation, vascular aneurysm, vulnerable plaque, chronic total occlusion, claudication, anastomotic proliferation for vein and artificial grafts, bile duct obstruction, urethra obstruction, tumor obstruction, and combinations thereof.

DETAILED DESCRIPTION OF THE INVENTION

Described in this invention is an elastin-based copolymer. The copolymer can be used to form a coating on a medical device. In some embodiments, the coating can further include a polymer, a biobeneficial material, a bioactive agent, or combinations of these. Some examples of the bioactive agent include, but are not limited to, paclitaxel, docetaxel, estradiol, nitric oxide donors, super oxide dismutases, super oxide dismutases mimics, 4-amino-2,2,6,6-tetramethylpiperidine-1-oxyl (4-amino-TEMPO), tacrolimus, dexamethasone, rapamycin, rapamycin derivatives, 40-O-(2-hydroxy)ethyl-rapamycin(everolimus), 40-O-(3-hydroxy)propyl-rapamycin, 40-O-[2-(2-hydroxy)ethoxy]ethyl-rapamycin, and 40-O-tetrazole-rapamycin, 40-epi-(N1-tetrazolyl)-rapamycin (ABT-578), pimecrolimus, imatinib mesylate, midostaurin, clobetasol, mometasone, bioactive RGD, CD-34 antibody, abciximab (REOPRO), progenitor cell capturing antibody, prohealing drugs, prodrugs thereof, co-drugs thereof, or a combination thereof.

A medical device having a coating described herein can be used to treat, prevent, or ameliorate a vascular medical condition. Some exemplary vascular medical conditions include atherosclerosis, thrombosis, restenosis, hemorrhage, vascular dissection or perforation, vascular aneurysm, vulnerable plaque, chronic total occlusion, claudication, anastomotic proliferation for vein and artificial grafts, bile duct obstruction, urethra obstruction, tumor obstruction, and combinations thereof

Elastin-Based Polymer

Elastin is a protein that is found in the walls of arteries, in lungs, intestines and skin in the body of an animal. Elastin imparts elasticity to the body. Working in partnership with collagen, elastin allows the body organs to stretch and relax. Thus, while collagen provides rigidity, elastin allows the blood vessels and heart tissues, for example, to stretch and then revert to their original positions.

Elastin is found to contain short peptides. The most frequent pentapeptide sequence is valyl-glycyl-valyl-prolyl-glycine (VGVPG). VGVPG is found to exhibit elastin-like properties (see, e.g., Reiersen, H., et al., J. Mol. Biol. 283:255-264 (1998)).

In some embodiments, the elastin-based polymer described herein can be an ABA or BAB type polymer, where A represents a unit that includes the pentapeptide sequence VGVPG and B represents a unit which can be a peptide sequence or a unit derived from a monomer. The copolymer can be a block or random copolymer.

In some embodiments, the elastin-based copolymer is an ABA triblock copolymer, where A is a block comprising the VGVPG sequence and B is a block derived from a peptide or monomer(s). In some embodiments, B can be a hydrophilic variant of the VGVPG peptide. The term “variant” refers to any form of VGVPG modification. For example, an amino acid in the peptide can be replaced with another amino acid. In some embodiments, the sequence of VGVPG can be varied so as to form a variant of the VGVPG peptide. In some embodiments, the VGVPG peptide can be modified to include lysine (lysine block). This lysine block can be used as the middle block to form the ABA triblock copolymer with the VGVPG pentapeptide. In these embodiments, the lysine block can be modified to conjugate a molecule or polymer such as phosphoryl choline (PC), poly(ethylene glycol) (PEG), or a bioactive moiety such as nitric oxide generating catalyst or TEMPO as pendant groups. These pendant groups can impart different physical, chemical, or biological properties to the elastin-based polymer.

As one of the properties for the natural elastin materials are usually non-degradable or very slow degradation, degradable linkages can be formed between the peptide blocks so that the newly formed elastin-based materials could be degradable. Any biodegradable polymers described below can be used as the linkage. Some examples of these degradable linkages are poly(lactic acid) (PLA), poly(glycolic acid) (PLGA), polycaprolactone (PCL), poly(3-hydroxybutyric acid (PHB), poly(4-hydroxybutyrate (P4HB), or combinations of these.

In some embodiments, the elastin-based copolymer is an ABA triblock copolymer where A is a block comprising the VGVPG peptide and B is a hydrophilic synthetic polymer. Such a synthetic polymer can be, for example, a hydrophilic polymer such as PEG, PVP (poly vinylpyrrolidinone), polyacrylamide, poly(PEG acrylate), poly (HEMA), poly(acrylic acid) or combinations of these polymers.

In some embodiments, the elastin-based copolymer is an ABA triblock copolymer where A is a block comprising the VGVPG peptide and B is a hydrophilic natural polymer such as protein or peptide. In some embodiments, such a hydrophilic natural polymer can be, for example, collagen or collagen derivative, hyaluronic acid, alginate or combinations of these.

In some embodiments, the elastin-based polymer can include a peptide sequence that promotes proliferation and/or migration of endothelial cells (ECs). Such peptide sequence can be, for example, RGD, cRGD, or EC specific sequences such as SIKVAV, CNP, YIGSRG, mimetics of these sequences, or combinations of these.

Composition of Elastin-Based Polymer

In some embodiments, the elastin-based polymer can be used in a composition for cell therapy carrier. For example, the composition can include the elastin-based polymer, cells such as stem cells and optionally other materials and agents. The composition can be delivered to a dysfunctional part of the body (e.g., an organ such as heart or blood vessel) while the cells are still viable. In some embodiments, the composition can include a pharmaceutically acceptable carrier.

Delivery of the composition can be achieved by any established modes of delivery. Preferably, the delivery can be injection or delivery through catheter. In some embodiments, the composition can also be delivered using surgical method such as creating a depot within the muscle and releasing the pharmaceutical agent(s) out of the depot.

Other Biocompatible Polymers

The elastin-based copolymer described herein can be used with other biocompatible polymers. The biocompatible polymer can be biodegradable (either bioerodable or bioabsorbable or both) or nondegradable and can be hydrophilic or hydrophobic. Representative biocompatible polymers include, but are not limited to, poly(ester amide), polyhydroxyalkanoates (PHA), poly(3-hydroxyalkanoates) such as poly(3-hydroxypropanoate), poly(3-hydroxybutyrate), poly(3-hydroxyvalerate), poly(3-hydroxyhexanoate), poly(3-hydroxyheptanoate) and poly(3-hydroxyoctanoate), poly(4-hydroxyalkanaote) such as poly(4-hydroxybutyrate), poly(4-hydroxyvalerate), poly(4-hydroxyhexanote), poly(4-hydroxyheptanoate), poly(4-hydroxyoctanoate) and copolymers including any of the 3-hydroxyalkanoate or 4-hydroxyalkanoate monomers described herein or blends thereof, poly(D,L-lactide), poly(L-lactide), polyglycolide, poly(D,L-lactide-co-glycolide), poly(L-lactide-co-glycolide), polycaprolactone, poly(lactide-co-caprolactone), poly(glycolide-co-caprolactone), poly(dioxanone), poly(ortho esters), poly(anhydrides), poly(tyrosine carbonates) and derivatives thereof, poly(tyrosine ester) and derivatives thereof, poly(imino carbonates), poly(glycolic acid-co-trimethylene carbonate), polyphosphoester, polyphosphoester urethane, poly(amino acids), polycyanoacrylates, poly(trimethylene carbonate), poly(iminocarbonate), polyphosphazenes, silicones, polyesters, polyolefins, polyisobutylene and ethylene-alphaolefin copolymers, acrylic polymers and copolymers, vinyl halide polymers and copolymers, such as polyvinyl chloride, polyvinyl ethers, such as polyvinyl methyl ether, polyvinylidene halides, such as polyvinylidene chloride, polyacrylonitrile, polyvinyl ketones, polyvinyl aromatics, such as polystyrene, polyvinyl esters, such as polyvinyl acetate, copolymers of vinyl monomers with each other and olefins, such as ethylene-methyl methacrylate copolymers, acrylonitrile-styrene copolymers, ABS resins, and ethylene-vinyl acetate copolymers, polyamides, such as Nylon 66 and polycaprolactam, alkyd resins, polycarbonates, polyoxymethylenes, polyimides, polyethers, poly(glyceryl sebacate), poly(propylene fumarate), poly(n-butyl methacrylate), poly(sec-butyl methacrylate), poly(isobutyl methacrylate), poly(tert-butyl methacrylate), poly(n-propyl methacrylate), poly(isopropyl methacrylate), poly(ethyl methacrylate), poly(methyl methacrylate), epoxy resins, polyurethanes, rayon, rayon-triacetate, cellulose acetate, cellulose butyrate, cellulose acetate butyrate, cellophane, cellulose nitrate, cellulose propionate, cellulose ethers, carboxymethyl cellulose, polyethers such as poly(ethylene glycol) (PEG), copoly(ether-esters) (e.g. poly(ethylene oxide-co-lactic acid) (PEO/PLA)), polyalkylene oxides such as poly(ethylene oxide), poly(propylene oxide), poly(ether ester), polyalkylene oxalates, phosphoryl choline containing polymer, choline, poly(aspirin), polymers and co-polymers of hydroxyl bearing monomers such as 2-hydroxyethyl methacrylate (HEMA), hydroxypropyl methacrylate (HPMA), hydroxypropylmethacrylamide, PEG acrylate (PEGA), PEG methacrylate, methacrylate polymers containing 2-methacryloyloxyethylphosphorylcholine (MPC) and n-vinyl pyrrolidone (VP), carboxylic acid bearing monomers such as methacrylic acid (MA), acrylic acid (AA), alkoxymethacrylate, alkoxyacrylate, and 3-trimethylsilylpropyl methacrylate (TMSPMA), poly(styrene-isoprene-styrene)-PEG (SIS-PEG), polystyrene-PEG, polyisobutylene-PEG, polycaprolactone-PEG (PCL-PEG), PLA-PEG, poly(methyl methacrylate)-PEG (PMMA-PEG), polydimethylsiloxane-co-PEG (PDMS-PEG), poly(vinylidene fluoride)-PEG (PVDF-PEG), PLURONIC™ surfactants (polypropylene oxide-co-polyethylene glycol), poly(tetramethylene glycol), hydroxy functional poly(vinyl pyrrolidone), molecules such as collagen, chitosan, alginate, fibrin, fibrinogen, cellulose, starch, dextran, dextrin, hyaluronic acid, fragments and derivatives of hyaluronic acid, heparin, fragments and derivatives of heparin, glycosamino glycan (GAG), GAG derivatives, polysaccharide, elastin, elastin protein mimetics, or combinations thereof. Some examples of elastin protein mimetics include (LGGVG)_(n), (VPGVG)_(n), Val-Pro-Gly-Val-Gly, or synthetic biomimetic poly(L-glytanmate)-b-poly(2-acryloyloxyethyllactoside)-b-poly(1-glutamate) triblock copolymer.

In some embodiments, the polymer can be poly(ethylene-co-vinyl alcohol), poly(methoxyethyl methacrylate), poly(dihydroxylpropyl methacrylate), polymethacrylamide, aliphatic polyurethane, aromatic polyurethane, nitrocellulose, poly(ester amide benzyl), co-poly-{[N,N′-sebacoyl-bis-(L-leucine)-1,6-hexylene diester]_(0.75)-[N,N′-sebacoyl-L-lysine benzyl ester]_(0.25)} (PEA-Bz), co-poly-{[N,N′-sebacoyl-bis-(L-leucine)-1,6-hexylene diester]_(0.75)-[N,N′-sebacoyl-L-lysine-4-amino-TEMPO amide]_(0.25)} (PEA-TEMPO), aliphatic polyester, aromatic polyester, fluorinated polymers such as poly(vinylidene fluoride-co-hexafluoropropylene), poly(vinylidene fluoride) (PVDF), and Teflon™ (polytetrafluoroethylene), a biopolymer such as elastin mimetic protein polymer, star or hyper-branched SIBS (styrene-block-isobutylene-block-styrene), or combinations thereof. In some embodiments, where the polymer is a copolymer, it can be a block copolymer that can be, e.g., di-, tri-, tetra-, or oligo-block copolymers or a random copolymer. In some embodiments, the polymer can also be branched polymers such as star polymers.

In some embodiments, a coating having the features described herein can exclude any one of the aforementioned polymers.

As used herein, the terms poly(D,L-lactide), poly(L-lactide), poly(D,L-lactide-co-glycolide), and poly(L-lactide-co-glycolide) can be used interchangeably with the terms poly(D,L-lactic acid), poly(L-lactic acid), poly(D,L-lactic acid-co-glycolic acid), or poly(L-lactic acid-co-glycolic acid), respectively.

Biobeneficial Material

The elastin-based copolymer can be optionally used with a biobeneficial material. The biobeneficial material can be a polymeric material or non-polymeric material. The biobeneficial material is preferably non-toxic, non-antigenic and non-immunogenic. A biobeneficial material is one which enhances the biocompatibility of the particles or device by being non-fouling, hemocompatible, actively non-thrombogenic, or antiinflammatory, all without depending on the release of a pharmaceutically active agent.

Representative biobeneficial materials include, but are not limited to, polyethers such as poly(ethylene glycol), copoly(ether-esters) (e.g. PEO/PLA), polyalkylene oxides such as poly(ethylene oxide), poly(propylene oxide), poly(ether ester), polyalkylene oxalates, polyphosphazenes, phosphoryl choline, choline, poly(aspirin), polymers and co-polymers of hydroxyl bearing monomers such as hydroxyethyl methacrylate (HEMA), hydroxypropyl methacrylate (HPMA), hydroxypropylmethacrylamide, poly(ethylene glycol)acrylate (PEGA), PEG methacrylate, 2-methacryloyloxyethylphosphorylcholine (MPC) and n-vinyl pyrrolidone (VP), carboxylic acid bearing monomers such as methacrylic acid (MA), acrylic acid (AA), alkoxymethacrylate, alkoxyacrylate, and 3-trimethylsilylpropyl methacrylate (TMSPMA), poly(styrene-isoprene-styrene)-PEG (SIS-PEG), polystyrene-PEG, polyisobutylene-PEG, polycaprolactone-PEG (PCL-PEG), PLA-PEG, poly(methyl methacrylate)-PEG (PMMA-PEG), polydimethylsiloxane-co-PEG (PDMS-PEG), poly(vinylidene fluoride)-PEG (PVDF-PEG), PLURONIC™ surfactants (polypropylene oxide-co-polyethylene glycol), poly(tetramethylene glycol), hydroxy functional poly(vinyl pyrrolidone), molecules such as fibrin, fibrinogen, cellulose, starch, collagen, dextran, dextrin, hyaluronic acid, fragments and derivatives of hyaluronic acid, heparin, fragments and derivatives of heparin, glycosamino glycan (GAG), GAG derivatives, polysaccharide, elastin, chitosan, alginate, silicones, PolyActive™, and combinations thereof. In some embodiments, a coating described herein can exclude any one of the aforementioned polymers. The term PolyActive™ refers to a block copolymer having flexible poly(ethylene glycol) and poly(butylene terephthalate) blocks (PEGT/PBT). PolyActive™ is intended to include AB, ABA, BAB copolymers having such segments of PEG and PBT (e.g., poly(ethylene glycol)-block-poly(butyleneterephthalate)-block poly(ethylene glycol) (PEG-PBT-PEG).

In a preferred embodiment, the biobeneficial material can be a polyether such as poly(ethylene glycol) (PEG) or polyalkylene oxide.

Bioactive Agents

The elastin-based copolymer can form a coating on a medical device. The coating can include one or more bioactive agent(s), which can be therapeutic, prophylactic, or diagnostic agent(s). These agents can have anti-proliferative or anti-inflammatory properties or can have other properties such as antineoplastic, antiplatelet, anti-coagulant, anti-fibrin, antithrombogenic, antimitotic, antibiotic, antiallergic, antifibrotic, and antioxidant. The agents can be cystostatic agents, agents that promote the healing of the endothelium such as NO releasing or generating agents, agents that attract endothelial progenitor cells, agents that promote the attachment, migration or proliferation of endothelial cells (e.g., natriuretic peptides such as CNP, ANP or BNP peptide or an RGD or cRGD peptide), while impeding smooth muscle cell proliferation. Examples of suitable therapeutic and prophylactic agents include synthetic inorganic and organic compounds, proteins and peptides, polysaccharides and other sugars, lipids, and DNA and RNA nucleic acid sequences having therapeutic, prophylactic or diagnostic activities. Some other examples of the bioactive agent include antibodies, receptor ligands, enzymes, adhesion peptides, blood clotting factors, inhibitors or clot dissolving agents such as streptokinase and tissue plasminogen activator, antigens for immunization, hormones and growth factors, oligonucleotides such as antisense oligonucleotides, small interfering RNA (siRNA), small hairpin RNA (shRNA), aptamers, ribozymes and retroviral vectors for use in gene therapy. Examples of anti-proliferative agents include rapamycin and its functional or structural derivatives, 40-O-(2-hydroxy)ethyl-rapamycin (everolimus), and its functional or structural derivatives, paclitaxel and its functional and structural derivatives. Examples of rapamycin derivatives include 40-epi-(N1-tetrazolyl)-rapamycin (ABT-578), 40-O-(3-hydroxy)propyl-rapamycin, 40-O[2-(2-hydroxy)ethoxy]ethyl-rapamycin, and 40-O-tetrazole-rapamycin. Examples of paclitaxel derivatives include docetaxel. Examples of antineoplastics and/or antimitotics include methotrexate, azathioprine, vincristine, vinblastine, fluorouracil, doxorubicin hydrochloride (e.g. Adriamycin® from Pharmacia & Upjohn, Peapack N.J.), and mitomycin (e.g. Mutamycin® from Bristol-Myers Squibb Co., Stamford, Conn.). Examples of such antiplatelets, anticoagulants, antifibrin, and antithrombins include sodium heparin, low molecular weight heparins, heparinoids, hirudin, argatroban, forskolin, vapiprost, prostacyclin and prostacyclin analogues, dextran, D-phe-pro-arg-chloromethylketone (synthetic antithrombin), dipyridamole, glycoprotein IIb/IIIa platelet membrane receptor antagonist antibody, recombinant hirudin, thrombin inhibitors such as Angiomax (Biogen, Inc., Cambridge, Mass.), calcium channel blockers (such as nifedipine), colchicine, fibroblast growth factor (FGF) antagonists, fish oil (omega 3-fatty acid), histamine antagonists, lovastatin (an inhibitor of HMG-CoA reductase, a cholesterol lowering drug, brand name Mevacor® from Merck & Co., Inc., Whitehouse Station, N.J.), monoclonal antibodies (such as those specific for Platelet-Derived Growth Factor (PDGF) receptors), nitroprusside, phosphodiesterase inhibitors, prostaglandin inhibitors, suramin, serotonin blockers, steroids, thioprotease inhibitors, triazolopyrimidine (a PDGF antagonist), nitric oxide or nitric oxide donors, super oxide dismutases, super oxide dismutase mimetic, 4-amino-2,2,6,6-tetramethylpiperidine-1-oxyl (4-amino-TEMPO), estradiol, anticancer agents, dietary supplements such as various vitamins, and a combination thereof. Examples of anti-inflammatory agents including steroidal and non-steroidal anti-inflammatory agents include tacrolimus, dexamethasone, clobetasol, mometasone, or combinations thereof. Examples of cytostatic substances include angiopeptin, angiotensin converting enzyme inhibitors such as captopril (e.g. Capoten® and Capozide® from Bristol-Myers Squibb Co., Stamford, Conn.), cilazapril or lisinopril (e.g. Prinivil® and Prinzide® from Merck & Co., Inc., Whitehouse Station, N.J.). An example of an antiallergic agent is permirolast potassium. Other therapeutic substances or agents which can be appropriate include alpha-interferon, pimecrolimus, imatinib mesylate, midostaurin, bioactive RGD, SIKVAV peptides, elevating agents such as cANP or cGMP peptides, and genetically engineered endothelial cells. The foregoing substances can also be used in the form of prodrugs or co-drugs thereof. The foregoing substances also include metabolites thereof and/or prodrugs of the metabolites. The foregoing substances are listed by way of example and are not meant to be limiting. Other active agents which are currently available or that may be developed in the future are equally applicable.

The dosage or concentration of the bioactive agent required to produce a favorable therapeutic effect should be less than the level at which the bioactive agent produces toxic effects and greater than non-therapeutic levels. The dosage or concentration of the bioactive agent can depend upon factors such as the particular circumstances of the patient, the nature of the trauma, the nature of the therapy desired, the time over which the administered ingredient resides at the vascular site, and if other active agents are employed, the nature and type of the substance or combination of substances. Therapeutically effective dosages can be determined empirically, for example by infusing vessels from suitable animal model systems and using immunohistochemical, fluorescent or electron microscopy methods to detect the agent and its effects, or by conducting suitable in vitro studies. Standard pharmacological test procedures to determine dosages are understood by one of ordinary skill in the art.

Coating of Elastin-Based Polymer

The elastin-based polymer can be coated on a medical device such as a stent according to an established coating process such as dipping, spray or other processes.

In some embodiments, the coating can be formed by dipping in an aqueous solution of the elastin-based polymer. For example, in some embodiments, a solution of an elastin-based polymer described here can be provided. A medical device such as a stent can be dipped in (rinsed) the solution at a temperature below ambient temperature (e.g., 4° C.). The rinsed medical device can be subject to heat treatment at a temperature in the range of about 15° C.-30° C. higher than the lower critical solution temperature (LCST) of the elastin-based polymer to generate a coating with biomimcry effect.

A solution of the elastin-based polymer can have a concentration of the polymer ranging from about 1 wt % to about 50 wt %. Preferably, the solution has a concentration of the elastin-based polymer in the range between about 5 wt % and about 30%, for example, about 10 wt %, about 15 wt %, about 20 wt % or about 25 wt %. The solution can include a solvent such as water or a biocompatible organic solvent such as dimethylformamide (DMF), dimethyl suloxide (DMSO), dimethyl acetamide (DMAC), methyl ethyl ketone (MEK), ethylene glycol or combinations of these.

In some embodiments, the solvent can be triflouroethanol (TFE). TFE has a boiling temperature of about 80° C., making the solvent a good solvent for use in coating a medical device. The concentration can be varied and determined according to the molecular weight of the elastin-based polymer for forming the coating. For example, with a elastin-based polymer with a weight average molecular weight about 160K Daltons, a solution of the polymer of about 2 wt % in TFE can be used to form a coating on a medical device using spray coating method at room temperature.

In some embodiments, the solution can be an acidic solution having a pH lower than 7. Where an acidic solution of the elastin-based polymer is used to form the coating on a medical device, medical device rinsed or sprayed with the acidic solution shall be rinsed (or sprayed) with a solution of basic pH (>7) buffered solution. Upon pH increase, the elastin-based polymer will come out of the solution and result in a coating on the medical device. The basic buffered solution can be any basic buffer solution in the art.

The mechanical property of the film cast from elastin-based polymer depends on the solution used in the cast. For example, for elongation of the film, generally a pH>7 coating system will lead to a higher elongation than a neutral or acidic water coating system, and a neutral or acidic water coating system will lead to a higher elongation than a TFE coating system.

Examples of Medical Device

As used herein, a medical device can be any suitable medical substrate that can be implanted in a human or veterinary patient. Examples of such medical devices include self-expandable stents, balloon-expandable stents, stent-grafts, grafts (e.g., aortic grafts), heart valve prostheses, cerebrospinal fluid shunts, electrodes, pacemaker electrodes, catheters, sensors, endocardial leads (e.g., FINELINE and ENDOTAK, available from Guidant Corporation, Santa Clara, Calif.), anastomotic devices and connectors, orthopedic implants such as screws, spinal implants, and electro-stimulatory devices. The underlying structure of the device can be of virtually any design. The device can be made of a metallic material or an alloy such as, but not limited to, cobalt chromium alloy (ELGILOY), stainless steel (316L), high nitrogen stainless steel, e.g., BIODUR 108, cobalt chrome alloy L-605, “MP35N,” “MP20N,”

ELASTINITE (Nitinol), tantalum, nickel-titanium alloy, platinum-iridium alloy, gold, magnesium, or combinations thereof. “MP35N” and “MP2ON” are trade names for alloys of cobalt, nickel, chromium and molybdenum available from Standard Press Steel Co., Jenkintown, Pa. “MP35N” consists of 35% cobalt, 35% nickel, 20% chromium, and 10% molybdenum. “MP20N” consists of 50% cobalt, 20% nickel, 20% chromium, and 10% molybdenum. Devices made from bioabsorbable or biostable polymers or bioabsorbable metals such as magnesium could also be used with the embodiments of the present invention. In some embodiments, the device is a bioabsorbable stent.

Method of Use

In accordance with embodiments of the invention, a medical device having a coating that includes the elastin-based polymer described herein can be used for treating, preventing or ameliorating a medical condition. Preferably, the medical device is a stent. The stent described herein is useful for a variety of medical procedures, including, by way of example, treatment of obstructions caused by tumors in bile ducts, esophagus, trachea/bronchi and other biological passageways. A stent having the above-described coating is particularly useful for treating diseased regions of blood vessels caused by lipid deposition, monocyte or macrophage infiltration, or dysfunctional endothelium or a combination thereof, or occluded regions of blood vessels caused by abnormal or inappropriate migration and proliferation of smooth muscle cells, thrombosis, and restenosis. Stents can be placed in a wide array of blood vessels, both arteries and veins. In some embodiments, the device described herein can be in dialysis, as grafts, or fistulae.

Representative examples of sites include the iliac, renal, carotid and coronary arteries.

For implantation of a stent, an angiogram is first performed to determine the appropriate positioning for stent therapy. An angiogram is typically accomplished by injecting a radiopaque contrasting agent through a catheter inserted into an artery or vein as an x-ray is taken. A guidewire is then advanced through the lesion or proposed site of treatment. Over the guidewire is passed a delivery catheter which allows a stent in its collapsed configuration to be inserted into the passageway. The delivery catheter is inserted either percutaneously or by surgery into the femoral artery, brachial artery, femoral vein, or brachial vein, and advanced into the appropriate blood vessel by steering the catheter through the vascular system under fluoroscopic guidance. A stent having the above-described features can then be expanded at the desired area of treatment. A post-insertion angiogram can also be utilized to confirm appropriate positioning.

While particular embodiments of the present invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications can be made without departing from this invention in its broader aspects. Therefore, the appended claims are to encompass within their scope all such changes and modifications as fall within the true spirit and scope of this invention. 

1.-40. (canceled)
 41. A method of forming a coating comprising an elastin-based copolymer on a medical device, comprising providing an acidic solution having pH below 7 comprising the elastin-based copolymer, applying the solution to the medical device to form a layer of the solution on the medical device, and applying a solution of buffer having a pH above 7 to the medical device to cause the elastin-based copolymer to come out to form the coating comprising the elastin-based copolymer.
 42. The method of claim 41, wherein the acidic solution further comprises a bioactive agent.
 43. The method of claim 42, wherein the bioactive agent is selected from the group consisting of paclitaxel, docetaxel, estradiol, 17-beta-estradiol, nitric oxide donors, super oxide dismutases, super oxide dismutase mimics, 4-amino-2,2,6,6-tetramethylpiperidine-1-oxyl (4-amino-TEMPO), tacrolimus, dexamethasone, rapamycin, 40-O-(2-hydroxy)ethyl-rapamycin (everolimus), 40-O-(3 -hydroxy)propyl-rapamycin, 40-O-[2-(2-hydroxy)ethoxy]ethyl-rapamycin, 40-O-tetrazole-rapamycin, 40-epi-(N1-tetrazolyl)-rapamycin (ABT-578), γ-hiridun, clobetasol, mometasone, pimecrolimus, imatinib mesylate, midostaurin, and combinations thereof.
 44. The method of claim 41, wherein the an elastin-based copolymer is a block copolymer comprising a block comprising an elastin pentapeptide (A) and a hydrophilic block (B), wherein the elastin pentapeptide is VGVPG (SEQ ID NO: 1).
 45. The method of claim 44, wherein the block copolymer is an ABA type triblock copolymer.
 46. The method of claim 44, wherein the hydrophilic block comprises lysine.
 47. The method of claim 44, wherein the hydrophilic block comprises a synthetic polymer.
 48. The method of claim 44, wherein the hydrophilic block comprises a natural polymer.
 49. The method of claim 44, wherein the hydrophilic block is a variant of the VGVPG (SEQ ID NO: 1).
 50. The method of claim 46, wherein the block copolymer further comprises a phosphoryl choline (PC) or poly(ethylene glycol) (PEG) pendant group, wherein the PC or PEG is conjugated to the block copolymer via lysine in the hydrophilic block.
 51. The method of claim 47, wherein the synthetic polymer is selected from the group consisting of PEG, PVP (poly vinylpyrrolidinone), polyacrylamide, poly(PEG acrylate), poly (HEMA), poly(acrylic acid), and combinations thereof
 52. The method of claim 48, wherein the natural polymer is selected from the group consisting of collagen or collagen derivative, hyaluronic acid, alginate, and combinations thereof.
 53. The method of claim 44, wherein the block copolymer further comprises a sequence that promotes proliferation and/or migration of endothelial cells.
 54. The method of claim 53, wherein the sequence is selected from the group consisting of RGD, cRGD, SIKVAV (SEQ ID NO: 2), CNP, YIGSRG (SEQ ID NO: 3), mimetics thereof, and combinations of thereof.
 55. The method of claim 44, wherein the block copolymer further comprises a biodegradable linkage between the A and B blocks.
 56. The method of claim 55, wherein the biodegradable linkage is selected from the group consisting of poly(lactic acid) (PLA), poly(glycolic acid) (PLGA), polycaprolactone (PCL), poly(3-hydroxybutyric acid (PHB), poly(4-hydroxybutyrate (P4HB), and combinations thereof.
 57. The method of claim 41, wherein the medical device is a stent.
 58. The method of claim 57, wherein the stent is a bioabsorbable stent. 